U.S. Pat. No. 1,219,796 describes a centrifugal filter having a casing accommodating a plurality of disk-like filtering elements which are in superimposed relation at a distance to each other and connected to a centrally extending hollow shaft. Each of the filtering elements consists of perforated plate covered by a wire mesh. Projecting into the space between two adjacent filtering elements are short pipes which extend radially and terminate adjacent the center of the casing. These pipes are provided with openings and communicate with an inlet pipe so as to allow the fluid to be filtered to be discharged into the interior of the casing and against the rotating filtering elements.
During the rotation of the filtering elements and of the fluid to be filtered, these short pipes cause turbulences by which dirt particles adhering to the surface of the elements are washed away.
The German patent publication DE-OS No. 2,507,762 discloses a filter including a plurality of coaxial and stationary disk-like filtering elements which are accommodated within a filter casing. The filter elements extend from the casing wall inwardly towards the hub of a rotor shaft which traverses the casing. Connected to the rotor shaft and extending between the filter elements are a plurality of rotating disks which may also be provided as disk-like filtering elements At their outer circumference, the disks are provided with vanes or blades Likewise, the stationary filtering elements may be provided with vanes or blades at the inner edge facing the hub.
These vanes or blades are provided to remove accumulation of solid materials from the outer periphery in the area of the inner wall of the casing as well as from the hub zone.
The German publication DE-AS No. 2,507,202 describes a similar filter in which the rotating disks are provided with curved vanes to provide the formation of a filter cake of predetermined thickness.
The filter described in the German publication No. 964,322 includes rotating disk-like filtering elements which are provided with vanes for stirring the bottom sludge.